The present invention relates to a die for forging a cylindrical rotor having thin, vane-accommodating grooves which extend inward from the periphery of the rotor, to a forging production system for producing the rotor, to a method for forging the rotor, and to the rotor.
Rotors have been employed in rotary compressors and vane pumps. Conventionally, rotors have been formed through the following method: aluminum alloy powder, an aluminum alloy cast material, or an extrusion material thereof is subjected to extrusion by use of an extrusion die as shown in FIG. 15 having portions that form vane-accommodating grooves (hereinafter referred to as xe2x80x9cvane-accommodating-groove-forming portionsxe2x80x9d or simply xe2x80x9cgroove-forming portionsxe2x80x9d) (151), and the thus-extruded preform is subjected to cutting; or a method as disclosed in Japanese Patent Application Laid-Open (kokai) No. 3-165948 in which an aluminum alloy material is subjected to forging by use of a die shown in FIG. 16, to thereby form a side wall of a cylindrical rotor and vane-accommodating grooves. When vane-accommodating grooves are formed through forging, in many cases, as shown in FIG. 17, a cylindrical portion (171) is provided at a position of a vane-accommodating-groove-forming portion which corresponds to the bottom of a vane-accommodating groove, in order to reduce stress concentration factor, form a relief of a working tool to thereby improve workability, and apply back pressure to a vane to thereby improve sealing performance.
When the aforementioned method in which an extruded preform is subjected to cutting is employed, since a material for a rotor to be extruded is easily twisted to thereby generate bending and warpage, possibly leading to failure to obtain dimensional accuracy in terms of straightness of a vane-accommodating groove which extends toward the axis of a rotor, excess working is required in order to obtain such dimensional accuracy, resulting in an increase in production costs. In addition, due to poor lubrication between the extrusion die and an aluminum alloy material, sticking and galling occur on the surface of the extrusion die, resulting in poor surface precision. Therefore, since excess working is required in order to attain high surface precision, production costs increase. When the extrusion die is employed, due to stress applied to the die, cracking is generated from sticking or galling occurring on the bottom of the groove-forming portions, thereby lowering durability of the die. In addition, since the shape of a chamfer (152), which is shown in greater detail in FIG. 1(B) and which is provided on the base of the groove-forming portion in order to prevent bending or breakage of the groove-forming portion, is reflected on the extruded rotor, machining for removing the resultant chamfer of the rotor is required in the subsequent step.
Meanwhile, when the aforementioned forging method is employed, the shape of a chamfer (172), which is provided on the base of a groove-forming portion of a forging die in order to prevent bending or breakage of the groove forming portion as in the case of the aforementioned extrusion die, is reflected on a forged product, and thus machining for removing the resultant chamfer of the forged product is required. Therefore, the resultant forged product (i.e., rotor) must be subjected to machining, resulting in high production costs. Since excess material (181) as shown in FIG. 18, which is required for working of the resultant chamfer, is removed, yield on the basis of the raw material is lowered, and production costs increase.
When a conventional forging die shown in FIG. 19 having no chamfer at a base (191) of a groove-forming portion is employed, during molding of a material, stress is applied to the base of the groove-forming portion, the groove-forming portion is bent, and dimensional accuracy in terms of straightness of a vane-accommodating groove is impaired. As a result, machining for obtaining such dimensional accuracy is required, and production costs increase. In addition, since the base of the groove-forming portion may be broken during forging in accordance with the degree of stress applied thereto, costs required for the die increase; i.e., production costs increase.
In order to solve dimensional-accuracy-related problems encountered by the aforementioned forging method, Japanese Patent No. 3127587 discloses a forging die including a die portion for forming a side wall of a cylindrical rotor and vane-accommodating-groove-forming portions, the groove-forming portions being formed separately from the die portion, and being shrunk on the die portion. However, since each of the groove-forming portions is supported merely by its base, considerable deviation of the groove-forming portion occurs during molding, thereby lowering dimensional accuracy of a vane-accommodating groove of the resultant forged product.
Meanwhile, in order to solve the mentioned accuracy-related problems, Japanese Patent Application Laid-Open (kokai) No. 2000-220588 discloses a mechanism in which vane-accommodating-groove-forming portions are provided on a punch, and deviation of the groove-forming portions is prevented by means of grooves for mating the groove-forming portions, the mating grooves being provided on a die. However, since a material intrudes into the mating grooves under application of pressure, and flash-shaped excess material which is formed through punching remains in vane-accommodating grooves of the resultant rotor, high production costs are required for removing the excess material.
In view of the foregoing, the present invention has been accomplished for solving the following problems: problems involved in an extrusion method; i.e., high production costs attributed to excess working required for producing vane-accommodating grooves of high accuracy; and problems involved in a forging method; i.e., high production costs attributed to excess working for removing excess material corresponding to the chamfer of vane-accommodating grooves, low dimensional accuracy of the vane-accommodating grooves, and generation of flash-shaped, excess material on the side wall of a rotor.
The present invention provides a forging die for producing a rotor of high dimensional accuracy at low cost, which die enables production of vane-accommodating grooves of high accuracy, and enables prevention or reduction of working required for removing chamfers of the vane-accommodating grooves. The present invention also provides a forging production system for producing the rotor; a method for producing the rotor; and the rotor.
The present inventors have performed extensive studies on the relation between a forging die and working accuracy of vane-accommodating grooves of a forged rotor product, thus leading to completion of the invention on the basis of their findings.
1) A first embodiment of the present invention for solving the aforementioned problems provides a forging die for forging a cylindrical rotor having a plurality of vane-accommodating grooves which extend toward an axis of the rotor, comprising an upper die; a lower die having a mold cavity in a center portion, and a plurality of vane-accommodating-groove-forming portions which protrude inward from an inner wall which defines the mold cavity; and a spacer having a plurality of shell segments for defining a shape of a side wall of the cylindrical rotor which is segmented by the vane-accommodating grooves, and a flange for joining the shell segments, the spacer being provided in the interior of the mold cavity of the lower die.
2) A second embodiment of the present invention for solving the aforementioned problems provides a forging die according to 1), wherein each of the shell segments of the spacer has an axial length equal to or greater than the axial length of the rotor and twice or less than twice the axial length of the rotor.
3) A third embodiment of the present invention for solving the aforementioned problems provides a forging die according to 1) or 2), wherein each of the shell segments of the spacer has a thickness {fraction (1/10)} to xc2xd the length of each of the vane-accommodating-groove-forming portions, the thickness being measured from the inner wall which defines the mold cavity toward the center of the spacer.
4) A fourth embodiment of the present invention for solving the aforementioned problems provides a forging die according to any one of 1) through 3), wherein a chamfer is provided between a base of each of the vane-accommodating-groove-forming portions and the inner wall which defines the mold cavity, and each of the shell segments of the spacer has a thickness 1 to 20 times the maximum curvature radius of the chamfer, the thickness being measured from the inner wall which defines the mold cavity toward the center of the spacer.
5) A fifth embodiment of the present invention for solving the aforementioned problems provides a forging die according to any one of 1) through 4), wherein a cylindrical protrusion having a maximum radius less than the distance between the center of the mold cavity and each of the vane-accommodating-groove-forming portions is provided on the center of the bottom surface of the lower die.
6) A sixth embodiment of the present invention for solving the aforementioned problems provides a forging die according to any one of 1) through 4), wherein a cylindrical protrusion having a maximum radius less than the distance between the center of the mold cavity of the lower die and each of the vane-accommodating-groove-forming portions is provided on a position of a surface of the upper die which faces the mold cavity, the position corresponding to the center of the bottom surface of the lower die.
7) A seventh embodiment of the present invention for solving the aforementioned problems provides a forging die according to any one of 1) through 6), wherein the upper die has a depression on a surface facing the mold cavity at a position which corresponds to each of the vane-accommodating-groove-forming portions, the depression being dented in a direction opposite the operation direction of the upper die.
8) An eighth embodiment of the present invention for solving the aforementioned problems provides a closed forging production system comprising an apparatus for cutting a material and a forging machine, wherein the forging machine includes a forging die as recited in any one of 1) through 7).
9) A ninth embodiment of the present invention for solving the aforementioned problems provides a method for producing an aluminum-alloy-made rotor, comprising forging a forging material into a rotor with a forging die as recited in any one of 1) through 7), an aluminum alloy cast bar, a material obtained through extrusion of an aluminum alloy cast bar, or a material obtained through extrusion of aluminum alloy powder, which serves as a forging material.
10) A tenth embodiment of the present invention for solving the aforementioned problems provides a cylindrical aluminum alloy rotor produced through forging, comprising a plurality of vane-accommodating grooves which extend toward an axis of the rotor, wherein the vane-accommodating grooves and a side wall of the cylindrical rotor which is segmented by the vane-accommodating grooves have no flash removal marks, and an edge portion formed by the segmented side wall and each of the grooves has a curvature radius of 0.5 mm or less.